1. Field of the Invention
The invention relates to an apparatus for liquefying a thermoplastic plastic, in particular an adhesive on the basis of polyurethane.
2. Description of the Prior Art
In such a liquefying apparatus as is known from U.S. Pat. No. 4,724,983 a heatable sealed supply container comprises an upper portion for receiving a downwardly open transport container for the thermoplastic plastic and a lower portion serving as buffer volume. A heating means integrated into the side walls of the supply container heats the thermoplastic plastic disposed in the transport container so that said plastic becomes liquid and drops into a base portion arranged in the supply container beneath the transport container and accomodating a collecting trough for the liquefied thermoplastic plastic. At the upper end of the supply container a pivotally formed cover is attached which is provided at its inner side with a mandrel; when the cover is closed the tip of the mandrel penetrates into the upwardly directed face of the transport container and thereby assists the flowing of the liquefied plastic out of the transport container.
Via a conduit an inert gas, usually serving as protective gas, can be supplied to the interior of the supply container.
In tests with such a liquefying apparatus it has however been found that the discharge speed of the molten plastic from the transport container is low so that the necessary amount of liquefied plastic is not made available reliably. In addition, reductions in the quality of the liquefied plastic can occur.